Alpha-core or perfect lay inductors for upgrading?

I'm trying to find out if one type of inductor is better suited for one application than for the mids and a different type for the woofers. Are Solen Hepta-litz air core one of the best available? How do they compare sound wise to Alpha-core inductors?
For what it's worth, I just used 10AWG air coils from North Creek to do Magnepan MG1.6. Good results. I considered various foil inductors, but they do have some reliability drawbacks, and I did hear that Magnepan discourages foil inductors. Lower AWG sizes (heavier wire size) are not available in foils. There may be significant differences between foil and wire, but similar size wire air coils should be equivalent (although the various manufacturers will argue otherwise).
Michael Percy sells silver ribbon air-core inductors.You will need to check with him for values.Might not get large enough for use in bass crossover.
I have used both Solen Hepta-link inductors and Alpha-core foil coils and prefer the later by a large margin. The solen's are a pain to use, stripping the laquer of all of the individual strands will take a lot of time and they are overall better performers then steel core inductors. However the goertz foil coils are amazing(for midrange and up) they add a palpable presence to the sound that no other inductor I have tried offers. They are natural sounding, fast, natural decay, I would recommend anyone to try them.

I would stay clear of Silver inductors for your first few projects for a few reason the price and the fact its MUCH harder to employ a silver inductor properly then a copper. They will sound better imediately however will have distortion in the upper octaves that will lead to fatigueing listening. If you need large value inductors for the bass I would stay away from air core coils, they do bizarre things to the signal from my experience. Not to mention a large air core coil will have a very large field that can effect all of the other coils near them. PRaT is compromised when using big values of air cores.

You can view my current crossover designs by clicking "My system" next to my moniker Tireguy and then click on the various crossover pictures. I am by no means an "expert" however I have tried more then a few different components to come up with the conclusions I have so far- next on the horizon for me is trying to implement bypass caps. which I feel may be the "trick" to great complicated crossover design's. Time will tell.
The Goertz will work better as frequency rises. They have less skin effect and time smear, which is why their mid and treble response are more coherent. I discussed many of these benefits in a recent Goertz speaker thread.

Having said that, if using the inductors as part of a low pass filter for a woofer, use the heaviest gauge quality built solid core inductor that you can find. Stranded wire offers less surface area and should be avoided if you're looking for best results.

El: Maggie probably recommends against the use of foil inductors because too many people are doing just that. That is, they are modifying their speakers using these specific parts. Asking a manufacturer for help improving their produce, who probably already thinks that their product is perfect, isn't typically going to get you an honest / unbiased answer most of the time. Sean
I would look at north creek music site and read all you can about coils they make a lot of good points.